It's a miracle that reboot-less updates mostly work in Linux. You need to restart services, etc. to make sure they have the latest libs. Gnome3+systemd does that now:

https://blogs.gnome.org/hughsie/2012/06/04/offline-os-update...

https://www.freedesktop.org/wiki/Software/systemd/SystemUpda...

https://fedoraproject.org/wiki/Features/OfflineSystemUpdates

It's still much faster than a Windows update (at least on my SSD system).